prospects of polarized fixed target drell-yan experiments

Prospects of Polarized Fixed Target Drell-Yan Experiments

Ming X. LiuLos Alamos National Laboratory

Key words: Transverse Single Spin Asymmetry (TSSA)

Drell-Yan (DY)

Ming X. Liu SPIN2010 2

Outline

• Physics Motivation

• Facilities and Experimental Challenges– Fermilab

• Current E906 – unpolarized DY • Future Polarized DY possibility

– RHIC • Current PHENIX/STAR • Future possibilities

– Polarized targets• J-Lab/UVA/SLAC

• Outlook


The Drell-Yan Process

2 2

21 2 1 2

1 2 1 2. .

4( ) ( ) ( ) ( )

9 a a a a aaD Y

de q x q x q x q x

dx dx sx x


Complimentality between DIS and Drell-Yan

Both DIS and Drell-Yan process are tools to probe the quark and antiquark structure in hadrons (factorization, universality)

DIS Drell-Yan

McGaughey, Moss, Peng,

Ann.Rev.Nucl. Part. Sci. 49 (1999) 217

Polarized DY NOT yet!Polarized DIS


Nucleon Structure @Leading Twist Collinear Approximation (I)

• Partonic interpretation of hard scatterings• Universal functions


Including kT … 5 more (II)

No K┴ dependence

K┴ - dependent

T-odd

K┴ - dependent

T-even


Transversity and TMDs can be probed via DY

1 1

1

- Unpolarized Drell-Yan:

- Single transverse spin asymmetry in polarized Drell

Boer-Mulders

-Yan:

cos

functions:

Sivers functions:

Transversity

(2 )

( ) ( )

distributio

DY

DYN T q q q

d h h

A f x f x

1 1

- Double transverse spin asymmetry in polarized Drell-Yan:

Drell-Yan and SIDIS involve different combinations of TMDs

Drell-Yan does not require

ns:

kno

( ) (

wledge of the fra

)DYTT q qA h x h x

gmentation functions

T-odd TMDs are predicted to change sign from DIS to DY

(Boer-Mulders and Sivers functions)

Remains to be tested experimenta ! lly


Color Flow in DY and DIS• The sign change – a new fundamental test of color gauge formalism

and factorization

Twist-3: sign change from gluonic-pole in hard parts

In the overlapped region – consistent description

Collins ‘02

Ji, Qiu, Vogelsang, Yuan ‘06Bacchetta, Boer, Diehl, Mulders ‘08


• Important test at RHIC of recent fundamental QCD predictions for the Sivers effect, demonstrating… attractive vs repulsive color charge forces

“Transverse-Spin Drell-Yan Physics at RHIC” (http://spin.riken.bnl.gov/rsc/write-up/dy_final.pdf)

0.1 0.2 0.3 x

Siv

ers

Am

plitu

de

HERMES

Sivers Asymmetries in SIDIS and DY


Sivers Functions and DY TSSA

• Expected AN of DY based on global fit to DIS fit of HERMES and COMPASS

Anselmino et al PRD 79 -54010(2009)


Importance of DY TSSA• Test the fundamental prediction of sign change in DY

TSSA compared to DIS based on our understanding of the origin of TSSA– Test of gauge formulism – Test of QCD factorization

• Help to resolve the proton spin puzzle?• One expect the observation of Sivers Asymmetry signals the

existence of partonic orbital angular momentum

f1T (x,kT )

SIDIS f1T

(x,kT )DY

1

2

1

2q Lq

z g Lgz

only ~30% of spinA future

challenge

Beginning to be measured at RHIC


Y. Goto 4/2010 CERN DY

- Polarized DY Dimuon Exp. at Fermilab Main Injector: 120GeV- RHIC fixed target possibility: 250 GeV

Proposed Future Polarized DY Exp’s


(I): E906 Drell-Yan

Polarized DY possibility:• Polarized targets • Polarize the Main

Injector • Or both• 120 GeV proton beam

4.9m

XBeam

XTarget


Polarized DY @Fermilab after E906 ?

• Transversely Polarized Targets– Sivers functions for quark and anti-quark– Test AN sign change

• Polarized Main Injector (A. Krisch & W. Lorenzon)– Polarized MI beam intensity

• 2.3x1012 p/pulse (w/ 2.8s/pulse) on E906 target, 51cm LH2• Lumi=1x1036/cm2/s

– Double spin asymmetry – possible

• Pion beam DY– Polarized target– Precision measurement of u,d-quark Siverse function


E906 Parameters @Fermilab• Beam energy = 120GeV• Beam structure and profile:

– 2x1012 protons/sec, for 5 sec/per min– Beam size: σx< 10mm and σy< 5mm, – Two years’ total = 7x1018, 15% efficiency

• Magnet: 8.4 T*m– pT kick ~ 2.5GeV

• Absorber: 15 λI, beam dump 30λI– Energy loss = 3.5GeV, E906 cut: p > 15GeV– Multiple scattering 170/p mr– Mass resolution = 240MeV @J/Psi

• Targets: < 15% λI – 50.8cm liquid hydrogen and deuterium– 12C, 56Fe, W

• 4<M<8 GeV– P1,2 > 0, 5, 10, 20 GeV– N = 5.3, 4.7, 3.5, 1.6 M dimuons– 50M DY, m>2GeV, sqrt(s)= 15 GeV

(L=900 fb-1 or 3.5x1016 pp)

Muons:P1,2 > 0,

5, 10, 20

xF = xBeam - xTarget


120 GeV @Main Injector

2 22

1 2 1 21 2 1 2. .

4( ) ( ) ( ) ( )

9 a a a a aaD Y

de q x q x q x q x

dx dx sx x

xBeam

xTarget

P>0 P>5

P>10 P>20

Anselmino et al PRD 79 -54010(2009)


DY Requires High Density Polarized Targets• DY dimuon production cross section small

- @120 GeV FixT (M>4) ~ 5 pb

• Solid Targets: possibleN

DY ~ 106 in ~1year, M> 4GeV

• Gas Targets: not likely

5.0~

2.0~

)%1.0

(~11

P

D

PDNPDA

DY

N

for an experimental precision of ~1%


UVA/J-Lab/SLAC Polarized proton/deuteron target

• Polarized NH3/ND3 targets• Dynamical Nuclear Polarization • Operate at 5 T and 1 K. Pol ~ B/T• Used with high beam intensities –

up to ~100 nA• Large capacity pumps• Polarizations:

– p > 90%, – d ~ 50%

• Able to handle high luminosity – up to ~ 1035 (Hall C)

~ 1034 (Hall B)

D. Crabb MENU10


Major Polarized Target SystemsD. Crabb MENU2010


Dynamic Nuclear PolarizationD. Crabb MENU2010


A. Krisch Fermilab 8/2010


Expected DY AN Sensitivity @120 GeV.

P(muon)>5 GeV

• Target- 6 cm NH3- 1019 proton


(II): Polarized DY w/ Fixed Target @RHIC ?

Polarized fixed target DY exp. with extracted polarized proton beams:

PHENIXSTA

R

BRAHMS

Fixed Target DY Exp. @Beam Dump

1. High density LH2/LD2 target

2. High density polarized targets

3 Map out x-dep.

- 250 GeV proton beams- Pol up to 70%


Proton Efficiency: Collider vs Fixed Target Mode (RHIC for e.g.)

• Design value: 2x1011x100 = 2 x 1013 proton per store per ring• Collision rate ~ 10 MHz

– Num. of collisions per store– 10M x 3600sec x 8 hr = 2.9 x 1010

– Fract. of p’s used = 3 x1011 / 2 x 1013 = 1.5 x 10-2

• In the fixed target mode, for a ~20% interaction length, we can use ~20% of the protons from the beam– 0.2/ 1.5 x 10-2 = 13x gain in luminosity

• Center of Mass Energies for p+p– Collider mode: sqrt(s) = 500 GeV– Fixted T mode: sqrt(s) = 22 GeV


Fixed Target @RHIC ?

• Beam dump experiment: dimuon channel– Parasitic mode

• Significant beams still left at the end of a store (~50%)• Cycle time ~8hr

– Dedicated fixed target• Cycle time ~ 1hr

– Dimu x-section @ 250 GeV (M>4) ~20pb

• Targets– E906-like unpolarized LH2 target

• 51cm LH2 (2.1x1024/cm2)• Can handle L ~ 1x1036cm-2s-1

– Polarized solid target• UVA/J-Lab/SLAC: L ~1035cm-2s-1

• Advantages– Polarized beams– (polarized) targets– Higher Energy and large x-coverage– High luminosity


250 GeV Polarized Beam Fixed T.X-Coverage

xBeam

xTarget

p>0 P>5GeV

P>10GeV P>20GeV


DY AN Sensitivity @250 GeV Fixed Target

• 4.5<M<8 GeV• qT < 1 GeV

• 10 fb-1

• 50 fb-1

xF


If Polarized Beam and Target …

1) Double-spin asymmetry (ALL) with longitudinally polarized beam/target in Drell-Yan probe quark helicity distributions

21 2 1 2

21 2 1 2

[ ( ) ( ) ( ) ( )]

[ ( ) ( ) ( ) ( )]a a a a aDY a

LLa a a a aa

e q x q x q x q xA

e q x q x q x q x

2) Double-spin asymmetry (ATT) with transversely polarized beam/target in Drell-Yan probe quark transversity distribution

21 1 1 2

21 2

( ) ( )ˆ

( ) ( )

q qqq

TT TTqq

e h x h xA a

e q x q x


Summary and Outlook• Pol. DY TSSA provides unique opportunity to study QCD spin

dynamics and nucleon structure

– Experimental test of the sign change will provide a critical test of our understanding of the origin of TSSA in QCD and the factorization

• Precision determination of the Sivers and other TMDs for both quark and anti-quark in a wide kinematic range.

• Polarized fixed target DY experiments could be realized at,– Fermilab– RHIC(w/ polarized targets)

• Collaboration: M.Bai, D. Crabb, J.Chen, Y. Goto, X.Jiang

Kang & Qiu PRD 81 (2010) 054020

Pbeam=250 GeV

Pbeam=120 GeV


• Topics:- Pol. DY Physics

- Pol. Beams - Pol. Targets

http://p25ext.lanl.gov/~ming/SantaFe-DY/Drell-Yan-Workshop.htm


Backup


Polarized Solid Target• Maximum beam current – UVA/JLAB/SLAC target

– Up to ~100nA = 6.2x1011p/s -> maximun lumi = 1035

– E906: 1x1013ppp (5 sec slow extraction, spill/min)=>320 nA (5sec avg), or 27nA(avg over 1 minute)=>L = 3.4 x 1035 cm-2s-1

– J-PARC: 5x1012ppp = 2.5x1012x2 sec per pulse I= 403 nA (2 sec avg)

– RHIC: 2x1011/bunch x 100 per store 2x1013 pps (1 hr to fill, compared to 1x1013 ppp 1 min per spill at Fermilab) A factor of 30 less than E906 in terms of total protons Make it 100nA = 200/6.2=32 sec slow extraction

• COMPASS NH3 target– Beam intensity up to 108/s, lumi = 1.7x1033

– Heat load ~2 mW – (refrigerator cooling power 5mW)

• E906 unpolarized LH2 target – E906: 51cm long => ~5% interaction length– Target limit: L = 1x1036 cm-2s-1 , ~3 times of E906 beam luminosity


Solid Target Mini Summary

• Mature Technology• Being used in other areas, eg MRI Studies; 13C• Proton Polarizations > 90%• Deuteron Polarizations > 70%• Nuclear Polarizations eg 6Li ~ 60%• Material studies eg CH3 , CH4 (irradiation)

• NMR improvements and modifications.


Meson East Spectrometer(E605/772/789/866)

Open-aperture Closed-aperture Beam-dump (Cu)

J/ΨJ/Ψ

Ψ’

σ(J/ψ) ~ 15 MeV σ(J/ψ) ~ 150 MeV σ(J/ψ) ~ 300 MeV


Hall A polarized 3He target

Both longitudinal, transverse and vertical

Luminosity=1036 (1/s) (highest in the world)

High in-beam polarization ~ 65%

Effective polarized neutron target

9 completed experiments 4 are currently running 6 approved with 12 GeV (A/C)

J. Chen


Theoretical Predictions for DY in pp

37

Kang & Qiu PRD 81 (2010) 054020

Anselmino, et al PRD 79 (2009) 054010

Fixed Target: p=250 GeV

Twist-3

TMD

Kang & Qiu PRD 81 (2010) 054020

prospects of polarized fixed target drell-yan experiments

Documents

liu spin2010ming

cern dy polarized dy

dy tssaexpected

importance of dy tssatest

polarized disming

drellyan processming

e906 target

e906 parameters